Field of the Invention
The invention concerns portable apparatus for discharging an air flow containing fluid droplets.
A device clamps onto the end of a discharge tube of a powered blower and discharges a fluid into the air flow. The fluid passes through a filter, an interchangeable flow limiting valve, and two successive constrictions.
The device provides for the control of flow, distribution and formation of spray droplets, within a size range considered as aerosols (<50 μm), specially aiming the control of current vector insects which transmit human disease epidemics and, manufactured for the assembly on powered backpack equipment for spraying/atomizing liquids, in such a way to allow the application in closed and difficult access areas, where motor vehicles are not able to arrive.
The device features, in its inner part, in the central part of the nozzle, a first constriction (venturi) which, through low pressure, allows the suction of the liquid leading into a next constriction where droplets are formed by disrupting the liquid surface tension in contact with the air stream.
Description of the Prior Art
In the current state of the art, several devices containing spray tips and nozzles are known.
The control of vector insects which transmit human diseases is a basic need in public health and, due to the possibility of epidemic outbursts of these insects, there must be control methods promptly available which allow a quick application, in an economic way and with elevated control efficacy.
The chemical control through the application of liquids delivered in the form of droplets is one of the most used methods for suppressing these insects. Within this method, the determination of the optimum size of the spray droplets and the use of equipment producing droplets within a narrow size range for the specific target will increment the biological efficacy of the pesticides, reduce the doses of the chemical products required and thus will minimize the environmental contamination.
Among the components of a spraying equipment, whether manual or powered, on land as well as aerial, the spraying tip is one of the main components, since they help in the determination of the outlet flow of the applied solution, are responsible for the way of delivery of the liquid and the size of droplets generated in the spraying process. There are different types of tips, and they are classified according to the main energy source utilized for the liquid spraying, which may be hydraulic, when the liquid is sprayed under pressure, or pneumatic, when the liquid is sprayed by action of a gas or steam, or even centrifugal, when the energy of a revolving mechanism is used, among others.
Currently a great variety of spraying tips which utilize the pneumatic method for generation of droplets is known, but few of them achieve them in the form of aerosols (<50 μm), due to design deficiencies, both in the dimensioning and in the adequate harmonization with the other components of a spraying equipment, such as for example, the fan or air blower, common in backpack sprayers, which must generate an adequate air flow for the formation of droplets.
The pneumatic backpack sprayers for use in public health in the control of epidemics of insects transmitting diseases (such as dengue, malaria and yellow fever), require application of insecticides in the form of aerosols, in ultra low volume (ULV) and low volume (LV), which makes the droplets keep in suspension for a determined period, so that the insects may get in contact and absorb such droplets, since larger droplets are not absorbed by these insects due to their minute size. So, droplets in the aerosol range size have a direct consequence on the biological efficacy of the application.
Several powered backpack sprayers can be found in the market, which utilize a compressor, fan, or spinning blowers, generating a gas or air stream for splitting a liquid in the form of droplets, released from the end of a discharge tube. Powered backpack sprayers throw sprays horizontally at distances of 9 to 12 meters and vertically at 6 to 9 meters, but the performance of individual machines vary, depending on the engine and fan size and, the design efficiency.
The spraying tip is a key point in the efficiency of this design, and a large number of the ones existing in the market present the deficiency of lacking an elevated homogeneity in the spectrum of droplet size, within the adequate range for spatial treatments, in the control of flying vectors (<50 μm). And the types of tips which feature this homogeneity, which are the sprayers of the revolving type (revolving discs), generally show a limited dispersion of droplets, thus interfering with the efficiency when trying to reach difficult access sites, such as for example, in constructions, a common situation in public health applications.
Other places of spraying are equally known by the current art. Normally, means are used for constricting the passage of air, for spraying a liquid, by air induction, aiming to reduce the spray drift, which is the action of the wind on the droplets. Many of these known mechanisms use droplets sized not less than 150 microns, differently from the object of the present model.
Other mechanisms use Venturi type nozzles, but for spraying the droplets of liquids such as crops protection products, insecticides, among others, they feature complex constructions, with a great number of components, channels, holes, of difficult access and maintenance.